laico



March 3, 1964 J. P. LAICO 3,123,430

COAXIAL CABLE TERMINATION Filed Nov. 29, 1961 25 FIG? INVENTOR J. P. LA/CO ATTORNEY United States Patent O 3,123,431) COAXHAL CABLE TERMINATHON Joseph P. Laieo, Springfield, N.J., assignor to Bell Telephene Laboratories, Incorporated, New York, N.Y., a corporation of New York Filed Nov. 29, 1961, Ser. No. 155,661 1 Claim. (6!. 339-268) This invention relates to coaxial cables and more particularly to adjustable coaxial cable terminations.

The simplest type of coaxial cable termination is a simple short-circuit connection between the inner and outer conductors of the cable. For many purposes, it is desirable to adjust the axial location of such a shortcircuit termination. For example, in a traveling wave tube where wave energy is transferred from a coaxial cable to a conductive helix, the axial location of the termination of the coaxial cable is often adjustable manually to produce optimum matching conditions between the cable and the helix; the short-circuit termination effectively acts as a tuning plunger. Often, if the termination is readily movable it does not provide a dependable short-circuit connection.

It is an object of this invention to provide a readily adjustable and reliable short-circuit termination for a coaxial cable.

This and other objects of my invention are attained in an embodiment thereof comprising a coaxial cable having a hollow cylindrical outer conductor that coaxially surrounds a solid inner conductor. Two telescoping conductive sleeves are located in the space between the inner and outer conductors. Corresponding end portions of the two sleeves have tapered diameters such that one end of the inner sleeve constitutes a wedge between the outer sleeve and the inner conductor. The other end of the inner sleeve is threaded, and a nut thereon abuts against the outer sleeve. When the nut is tightened the wedge action between the two sleeves forces the outer sleeve tightly against the outer conductor and the inner sleeve against the inner conductor and a solid short-circuit between the inner and outer conductors is produced. The axial location of the termination can be adjusted by backing the nut off and manually moving the inner sleeve. The outer sleeve moves with the inner sleeve because it is contained between the nut and the wedge portion of the inner sleeve.

These and other objects and definitive features of my invention will be more fully appreciated from a consideration of the following detailed description, taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a sectional view of one embodiment of this invention;

FIG. 2 is an enlarged sectional view of the end portions of the conductive sleeves of the device of FIG. 1;

FIG. 3 is a view of the inner sleeve of the device of FIG. I; and

FIG. 4 is a view of the outer sleeve of the device of FIG. 1.

Referring now to FIG. 1, there is shown a coaxial cable comprising an inner conductor 11 and a hollow cylindrical outer conductor 12. Only the terminal end of the coaxial cable is shown. In accordance with the invention, a short-circuit connection between inner conductor 11 and outer conductor 12 is effected by two hollow con ductive sleeves 14 and 15.

Sleeves 14 and 15 are both substantially cylindrical and are coaxial with inner conductor 11. As can be best seen in FIG. 2, the diameters of the two sleeves are tapered toward the outer conductor 12 so that the outer surface of inner sleeve 14 takes the form of a Wedgeshaped flange 19.

The other end of sleeve 14 is threaded to receive an adjusting nut 20. When nut 20 is rotated so as to move axially toward the left as shown by arrow 21, it abuts against outer sleeve 15 and tends to push outer sleeve 15 toward the left while pulling inner sleeve 14 toward the right as shown by the arrows in FIG. 2. The wedge action between sleeves 14 and 15 presses outer sleeve 15 firmly against outer conductor 12., and inner sleeve 14 against inner conductor 11. Hence, by tightening nut 29 against outer sleeve 15, a firm and reliable short-circuit termination is produced between the inner and outer conductors of the coaxial cable. A typical angle of taper of wedge portion 19 is 30 degrees, although other angles could be used.

A locked nut 23 is included as a handle at the extreme end of the threaded portion of inner sleeve 14. When one wishes to adjust the axial position of the termination produced by sleeves 14 and 15, he grasps locked nut 23 in one hand and backs nut 20 off from outer sleeve 15 with the other hand. The stresses on the sleeves are thereby removed and the axial position of the sleeves can be adjusted by axially moving locked nut 23. Of course, it is not necessary to include nut 23 in the device, but since inner sleeve 14 must be threaded to receive nut 21), it makes a convenient handle. Nut 23 is locked in position by a set-screw 24.

As can be seen in FIGS. 3 and 4, sleeves 14 and 15 each have two pairs of slots 25 extending along a corresponding end portion. The purpose of these slots is to relieve stress on the sleeves when nut 20 is tightened.

From the foregoing discussion, it can be appreciated that my adjustable termination is of simple structure and easily manufactured, while being reliable and easy to use. It may be used in any of numerous circuits where simple manual adjustment of the electrical length of a coaxial cable is desired. However, the described embodiment is only intended to be illustrative of my invention; various other arrangements may be made without departing from the spirit and scope of the invention.

What is claimed is:

A device for selectively short circuiting the inner and outer conductors of a coaxial cable at any desired longitudinal position therealong consisting solely of:

an inner conductive sleeve located between the inner and outer conductors of the coaxial cable;

an outer conductive sleeve located between the inner conductive sleeve and the outer conductor of the coaxial cable;

the outer conductive sleeve extending out one end of the coaxial cable;

the inner conductive sleeve extending out the said one end of the coaxial cable beyond the outer conductive sleeve;

the portion of the inner conductive sleeve that extends beyond the outer sleeve being threaded;

the end of the inner sleeve opposite the threaded por- '3 4 tion being flared to form a wedge around the outer a first nut being located on the threaded portion of circumference thereof; the inner sleeve and being adapted to abut against the surfaces of the inner sleeve between the flared end one end of the outer sleeve;

and the threaded end being Smooth and subsifiniially a second nut being located on the end of the threaded cylindrical; V 5 portion of the inner sleeve; One end of the Outer Sleeve being adjacent the flared and a set screw in the second nut for restraining its end of the inner sleeve and having an inner surface rot tion with respect to the threaded portion.

that is tapered to bear flush against the circumferential Wedge of the inner Sleeve; References Cited in the file of this patent all of the remaining surfaces of the outer sleeve be- 10 UNITED STATES PATENTS tween its two ends being smooth and substantially 2644929 K f July 7 5 cylmdl'lcal; 2,763,845 Laube Sept 18, 1956 

